KR20080040316A - The plate for brightness enhancement - Google Patents

Abstract

A luminance enhancement plate is provided to reduce a manufacturing cost of an optical device like a backlight unit by minimizing used optical films or prism sheets doubling luminance. A luminance enhancement plate is composed of a diffusion layer(10), an air layer(20) formed on one surface of the diffusion layer, and a prism layer(30) formed on one surface of the air layer. The prism layer contains prism making solution and beads(33). Difference between the refractive indexes of the prism making solution and the bead is below 0.06. The refractive index of the prism making solution is over 1.52. The prism layer has a base layer(31) with thickness over 25 to 300um. The beads are formed on one or both surfaces of the base layer of the prism layer or included in the prism making solution.

Description

Plate for brightness enhancement

1 is a cross-sectional view showing a preferred embodiment of the present invention;

2 is a cross-sectional view showing another preferred embodiment of the present invention;

3 is a cross-sectional view showing another preferred embodiment of the present invention.

[Description of main part of drawing]

10: diffusion layer 20: air layer

21: support portion 22: through hole

30: prism layer 31: base material layer

32: prism pattern layer 33: beads

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plate for improving luminance used in a backlight unit, a lighting device, or the like of a liquid crystal display.

The backlight unit (BLU), which is widely used in liquid crystal displays, uses light sources such as Cold Cathode Fluorescent Lamps (CCFLs) to sequentially pass through the light guide plate, the light diffusion plate, and the prism sheet to the liquid crystal panel. To reach. The light emitted from the light source is distributed to the front surface of the flat liquid crystal panel through the light guide plate, and the light source passed through the light guide plate can obtain a uniform light intensity across the entire screen through the light diffusion plate. The optical path control function is performed to convert the light beams in various directions through the diffusion sheet into the viewing angle range suitable for the viewer to recognize the image. In addition, the lower portion of the light guide plate is provided with a reflecting plate for increasing the use efficiency of the light source by allowing the light that is not delivered to the liquid crystal panel to be reflected back out of the path and used.

In addition, many kinds of plates or films are used so that the maximum amount of light generated from the light source can reach the liquid crystal device.

The light diffusion plate achieves a uniformity of brightness of the light emitted from the light source lamp and at the same time serves as a concealing role to cover the bright line of the lamp. In addition, it serves as a support for the above various optical films. To this end, various light diffusing agents are added to the light diffusing plate, which causes light diffraction, scattering, reflection, and the like, and causes a diffusion effect.

In order to collect a large amount of light from the light diffusion plate to the front, a variety of materials including a light diffusion film, a prism film should be mounted, and the multi-layered material raises the unit cost and decreases productivity. It is becoming.

In recent years, attempts have been made to reduce the application of optical films used in order to simplify the production process, for example, bonding a prism sheet onto a light diffusion plate. However, in this case, there is a problem that a stain occurs due to the adhesive when the light diffusion plate and the prism sheet are attached. Therefore, it is necessary to give the effect of masking such a stain on the prism sheet, in this case there is a problem that the brightness is reduced.

Accordingly, the inventors of the present invention have confirmed that the present invention can provide a brightness enhancement plate that minimizes the decrease in brightness while effectively masking stains generated when the light diffusing plate and the prism sheet are adhered while minimizing the application of optical films. .

Accordingly, an object of the present invention is to provide a plate for improving brightness while effectively covering adhesive stains.

In addition, an object of the present invention is to provide a plate for improving brightness that can minimize the application of additional optical films included.

The present invention for achieving the above object is a diffusion layer; An air layer formed on one surface of the diffusion layer; And a prism layer formed on one surface of the air layer, the prism layer including a prism crude liquid and a bead having a refractive index difference of about 0.06 or less.

The prism crude liquid has a refractive index of 1.52 or more.

The prism layer is characterized in that it comprises a base layer having a thickness of 25 ~ 300㎛.

The beads may be formed on one side or both sides of the base layer in the prism layer or included in the prismatic liquid.

The beads are characterized in that the particle diameter of 2 ~ 30㎛.

The bead is characterized in that at least one selected from acrylic beads, styrene beads and acrylic-styrene beads.

The bead is characterized in that 1 to 50 parts by weight based on 100 parts by weight of the prism crude liquid.

The air layer is characterized in that it comprises a support and a through-hole.

Hereinafter, with reference to the accompanying drawings will be described the present invention in more detail.

1 to 3 illustrate an embodiment of the luminance improving plate of the present invention, and the luminance enhancement plate in which the air layer 20 and the prism layer 30 are sequentially formed on one surface of the diffusion layer 10 and the diffusion layer 10. An example is shown.

The prism layer 30 includes a base layer 31, a prism pattern layer 32, and beads 33. At this time, the bead 33 may form a prism pattern layer 32 on one surface of the substrate layer 31 and coat it on the back surface, as shown in FIG. 1, or as shown in FIG. 2. The prism pattern layer 32 may be formed on one surface and the same surface. Also, the beads 33 may be coated on both sides of the base layer 31 (not shown), and as shown in FIG. 3, the beads 33 may be mixed with the prismatic liquid forming the prism pattern layer 32. The prism pattern layer 32 may be formed.

When the beads 33 are formed on one or both surfaces of the base layer 31, the binder is selected and coated in consideration of compatibility with the beads 33. It is preferable to use at least one selected from the group consisting of acrylic beads, styrene beads, and acrylic-styrene beads in consideration of the refractive index, and the binder 33 may be one or more selected from acrylic, urethane, and epoxy. Among them, acrylic type is most preferred. The coating method of the beads 33 is not particularly limited. It is advantageous that the beads 33 have a particle diameter of 2 to 30 μm in terms of preventing luminance unevenness. Preferably, in consideration of the particle diameter of the bead 33, the thickness of the bead 33 coating layer is preferably 5 ~ 50㎛.

The prism layer 30 may have a lower refractive index than when the prism sheet is used alone. If the refractive index of the prism solution is 1.52 or more, sufficient brightness improvement can be seen. The refractive index of the prismatic liquid solution was measured by dropping two or three drops of the crude liquid after setting the temperature at 25 ° C. using an Abe refractometer (manufacturer: ATAGO, model name: 4T).

The composition of the prism crude liquid used for the prism pattern layer 30 is not particularly limited, and conventionally known resins used for a prism sheet or a prism film can be used. For example, the composition may include a mixture of a monomer or oligomer for ultraviolet polymerization and a photoinitiator.

Preferably, the beads 33 have a refractive index difference of 0.06 or less from that of the prismatic liquid forming the prism pattern layer 32. If the difference in refractive index is larger than 0.06, there is a problem in that the plate becomes too cloudy and the degree of deterioration of luminance is increased. The smaller the difference in refractive index is, the lower the decrease in luminance is. Therefore, there is no meaning to limit the lower limit of the difference in refractive index between the bead 33 and the prism solution.

On the other hand, even when the beads 33 having no difference in refractive index with the prism liquid are used, the luminance is reduced. Therefore, it is necessary to adjust the content of the beads 33 in order to minimize the decrease in brightness, it is preferable to use 1 to 50 parts by weight based on 100 parts by weight of the prism crude liquid.

As such, by including the beads 33 having a refractive index difference of 0.06 or less with the prismatic liquid solution, the total light transmittance can be adjusted while maintaining the concealability, so that the adhesion of the diffusion layer 10 and the prism layer 30 occurs while minimizing the application of optical films The stain can also be covered.

And the base material layer 31 of the prism layer 30 may be thinner than the case where a prism sheet is used independently. Conventionally, the sheet was thick because it must be flattened, but the plate in the present invention is because the diffusion layer 10 already has a sufficient thickness. Therefore, the thickness of the base material layer 31 should just be 25-300 micrometers. The base material layer 31 can be used as long as it is a transparent resin used in a conventional prism sheet or prism film, for example, polyethylene terephthalate film, polycarbonate film, polypropylene film, polyethylene film, polystyrene film or polyepoxy film. It may be selected from the group.

The prism pattern layer 32 may have a polygonal, semi-circular or semi-elliptic polyhedron cross section, or may have a polygonal, semi-circular or semi-elliptic columnar cross section, and the shape may be formed in one or more types. have. Also, each structure may or may not be adjacent to each other. The prism pattern layer 32 as described above increases the brightness by collecting the diffused light to the front part by controlling the optical path.

On the other hand, the formation method of the air layer 20 is not specifically limited. For example, by applying a photosensitive material to form lithography, the support part 21 is formed to be spaced at a predetermined interval, or the surface of the substrate layer 10 is cut by a method such as laser processing to be spaced at a predetermined interval to form the through portion 22. Alternatively, the air layer may be formed using a method of laminating an ultraviolet curable resin on one surface of the air layer, dipping the mold into an uneven mold, and then curing the ultraviolet ray.

The uneven structure of the air layer 20 allows the diffusion layer 10 formed on the lower layer of the air layer 20 and the prism layer 30 formed on the upper surface of the air layer 20 to be contacted with only the support part 21. It has a structure through which air passes through the through part 22 of 20.

In the conventional light diffusion plate manufacturing, in order to improve brightness, irregularities are formed on the surface by containing light diffusing particles, but the size of the particle is limited in consideration of compatibility with the base resin used in the light diffusion plate. Therefore, when the prism layer was formed on the light diffusing plate, the through hole 22 was not formed even when the light diffusing particles were used as large as possible.

Accordingly, by separately forming the air layer 20 in which the through-holes 22 are stably formed as in the present invention, the luminance-enhancing plate has a relatively low-density through-hole 22 formed of air having light diffused sufficiently from the diffusion layer 10. After passing through, it moves to the relatively high density prism layer 30, and the light is effectively collected by the light recycling and light refraction which are inherent functions of the prism layer, thereby improving brightness.

Therefore, the air layer 20 is formed between the diffusion layer 10 for diffusing light and the prism layer 30 for collecting light, thereby effectively improving luminance, and providing a conventional diffusion film and a prism sheet as a single plate for improving luminance. Therefore, the number of films to be mounted on the backlight unit can be reduced, and the luminance can be improved to be equal to or greater than that of a conventional light diffusing plate and prism sheet.

It is sufficient that the air layer 20 has a height that allows air to pass through.

On the other hand, the composition of the base resin used in the diffusion layer 10 is not particularly limited, it is possible to use a known base resin used in the conventional light diffusion plate. For example, polymethyl methacrylate resin, polystyrene resin, polycarbonate resin, styrene-acrylic copolymer resin, etc. are mentioned.

The thickness of the diffusion layer 10 is preferably 0.8 ~ 2.0mm.

The diffusion layer 10 may further include a light diffusing agent, and various organic and inorganic particles used in the conventional light diffusing plate may be used as the light diffusing agent.

Representative organic particles include methyl methacrylate, ethyl methacrylate, isobutyl methacrylate, normal butyl methacrylate, normal butyl methyl methacrylate, acrylic acid, methacrylic acid and hydroxyethyl methacrylate. , Hydroxypropyl methacrylate, hydroxy ethyl acrylate, acrylamide, methyl acrylamide, glycidyl methacrylate, ethyl acrylate, isobutyl acrylate, normal butyl acrylate, 2-ethylhexyl acrylate, styrene And acrylic polymer particles such as substituted styrene polymers or copolymers or terpolymers thereof; Styrenic polymer particles; Olefin polymer particles such as polyethylene and polypropylene; Copolymer particles of acryl and styrene; Copolymer particles of acryl and olefins; Styrene and olefin copolymer particles; Multi-layered multicomponent particles made by forming the particles of the homopolymer, copolymer or terpolymer and then covering the layers with other types of monomers; Siloxane-based polymer particles; Fluorine resin particles and the like.

On the other hand, examples of the inorganic light diffusing agent include calcium carbonate, barium sulfate, silicon oxide, aluminum hydroxide, titanium oxide, zirconium oxide, magnesium fluoride, talc, glass, mica and the like. Normally, the organic particles have excellent light diffusivity compared to inorganic particles, and if necessary, two or more kinds of light diffusing agents can be used in combination.

At this time, the light diffusing agent exhibits a light diffusing effect even in a small amount when the refractive index with the base resin is large, and a relatively large amount should be included when the refractive index difference is small.

In addition, if the content of the light diffusing agent is too high may cause a phenomenon that the brightness is rather deteriorated, by controlling the content of the light diffusing agent may exhibit a high brightness characteristics while showing the appropriate concealability.

In consideration of the above, the content of the light diffusing agent may be preferably 10 parts by weight or less based on 100 parts by weight of the base resin. And the particle diameter of the light diffusing agent may be considered 100㎛ or less.

In addition, the processing stabilizer, ultraviolet absorber, ultraviolet stabilizer, etc. may be added to the brightness improving plate of the present invention as necessary.

Although the present invention has been described with reference to the accompanying drawings, the present invention is not limited thereto, and a person skilled in the art may change the present invention without departing from the technical spirit of the present invention. Do.

Hereinafter, examples of the present invention will be described in more detail, but the scope of the present invention is not limited to these examples.

<Example 1>

The support part of the rectangular parallelepiped pattern was formed by roll patterning on one surface of the 2.0-mm-thick diffusion layer containing 100 weight part of polymethyl methacrylate resins, and 1 weight part of silicone resin beads with a particle diameter of 2 micrometers.

On the upper surface of the support portion, a polyethylene terephthalate base layer having a thickness of 188 μm is mixed with 100 parts by weight of an acrylate oligomer (refractive index: 1.57) and 30 parts by weight of styrene beads having a particle diameter of 10 μm and a refractive index of 1.59 by triangular prism pattern layer by UV curing. The formed film was bonded to prepare a plate for improving brightness. (See Figure 3)

<Example 2>

The configuration of the diffusion layer and the formation of the supporting portion are the same as in Example 1. Form a prism pattern layer using an acrylate oligomer (refractive index: 1.57) on a polyethylene terephthalate base layer having a thickness of 188 μm, and mix 30 parts by weight of 10 μm styrene beads (refractive index: 1.59) with the acrylate oligomer crude solution on the opposite side. After coating 25㎛ thickness was bonded to the upper surface of the support to prepare a plate for improving brightness. (See Figure 1)

<Example 3>

Except for coating a styrene bead on the polyethylene terephthalate base layer in Example 2 to form a prism pattern layer and to form a prism layer was formed in the same manner except that the prism layer. (See Figure 2)

<Example 4>

Except for using a styrene beads of 20 ㎛ particle diameter in Example 1 instead of the styrene beads of 10 ㎛ particle size, a plate for improving brightness was prepared in the same manner.

<Example 5>

Except for using styrene beads in Example 1 acrylic-styrene beads having a refractive index of 1.51 was prepared in the same manner as the brightness enhancement plate.

<Example 6>

Except that the styrene bead content in Example 1 to 1 part by weight was prepared a brightness improving plate in the same manner.

<Example 7>

Except that the styrene bead content in Example 1 to 50 parts by weight, a brightness improving plate was prepared in the same manner.

<Example 8>

Except for changing the styrene bead content in Example 1 to 70 parts by weight, a plate for improving brightness was manufactured.

Example 9

Except for using a polyethylene terephthalate base layer having a thickness of 128㎛ in Example 1 was prepared a plate for improving brightness.

<Example 10>

Except for using a polyethylene terephthalate base layer having a thickness of 50㎛ in Example 1 was prepared a plate for improving brightness.

Comparative Example 1

Except for using methacrylate methyl methacrylate beads (refractive index: 1.49) in Example 1 was prepared in the same manner as for improving the brightness.

Comparative Example 2

Except for using the silicon beads (refractive index: 1.42) instead of styrene beads in Example 1 was prepared a plate for improving brightness.

Comparative Example 3

Except that styrene beads were not used in Example 1, a plate for improving brightness was manufactured.

The luminance and visual stain test was performed on the luminance improving plate manufactured in the above embodiment in the following manner, and the results are shown in [Table 1].

(1) luminance

Luminance was measured after the backlight was turned on using Topcon's BM-7, the diffuser plate was put on, and preheated for two hours.The value was removed by removing all the sheets except the reflective sheet in the backlight unit (BLU, 26 inches) and simply Sumitomo. The luminance value of the luminance enhancing plates produced by the above Examples and Comparative Examples was measured in terms of the luminance increase (without the liquid crystal panel) when the diffuser plate of RM714 was used.

(2) visual stain inspection

Visual staining was visually evaluated while the LCD panel was put on and operated after assembly of the backlight unit (BLU). When staining was not seen, it was marked as good and staining was marked as bad.

division Luminance (%) Visual stain test Example 1 48 Good Example 2 45 Good Example 3 46 Good Example 4 45 Good Example 5 38 Good Example 6 52 Good Example 7 41 Good Example 8 35 Good Example 9 49 Good Example 10 50 Good Comparative Example 1 34 Good Comparative Example 2 22 Good Comparative Example 3 55 Bad

*% Luminance is increased compared to RM714

As a result of the property evaluation, the larger the difference in refractive index between the prismatic liquid and the bead is not sufficient in terms of increasing the brightness. When manufacturing an integrated diffuser plate alone without the addition of beads alone, it is advantageous in terms of brightness, but there is a problem that the stain is visible as it is visually inspected after assembling the liquid crystal panel. Therefore, it is most preferable to add beads having a refractive index difference of 0.06 or less to the prism crude liquid in terms of increasing luminance and preventing adhesion staining. In addition, it can be seen that the total light transmittance can be adjusted while maintaining appropriate concealment.

As described above, the present invention can provide a brightness improving plate excellent in brightness while effectively covering the adhesive stain.

Accordingly, the present invention minimizes the necessity of additionally providing additional optical films or prism sheets for doubling the luminance by providing a plate having sufficiently high luminance, and thus, it is possible to manufacture an optical device such as a backlight unit at low cost.

In addition, the present invention can control the total light transmittance while maintaining the concealment, it is possible to manufacture an optical device such as a backlight unit at low cost without laminating a separate optical film for concealment.

Claims (8)

Diffusion layer; An air layer formed on one surface of the diffusion layer; And And a prism layer formed on one surface of the air layer, the prism layer having a prism solution and a bead having a refractive index difference of 0.06 or less. The method of claim 1, The prism crude liquid has a refractive index of at least 1.52. The method of claim 1, The prism layer includes a substrate layer having a thickness of 25 to 300 μm. The method according to any one of claims 1 to 3, Beads are formed on one side or both sides of the base layer in the prism layer or included in the prismatic liquid solution. The method of claim 1, The bead is a brightness enhancement plate, characterized in that the particle diameter of 2 ~ 30㎛. The method of claim 1, The bead is a brightness improving plate, characterized in that at least one selected from acrylic beads, styrene beads and acrylic-styrene beads. The method of claim 1, Bead is 1 to 50 parts by weight based on 100 parts by weight of the prism crude liquid. The method of claim 1, The air layer is a brightness enhancement plate comprising a support and a through-hole.

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